1. Field of Invention
This invention relates to electronic devices such as, for example, transistors and methods for fabricating the same.
2. Description of Related Art
Electronic devices, such as, for example, transistors, have a multitude of uses. For example, low cost, large area arrays of thin-film transistors (TFTs) are important components in flat panel displays, electric paper, and imagers. In a pixel of a display, a TFT is used as an electrical switch to charge a pixel electrode that switches the display media from one state to another. A display backplane comprises an array of pixel elements that is used to address the display media. Amorphous silicon is often used as the active material in TFTs for these applications.
Polymeric semiconductors have field effect mobilities of approximately 0.01-0.1 cm2V−1s−1 and are relatively simple to process due to their solubility and ease of forming continuous films. These field effect mobilities are typically lower than those obtained for amorphous silicon, ˜0.5-1.0 cm2V−1s−1.
Additive and subtractive patterning techniques are sometimes used to fabricate patterned polymeric TFTs. Additive methods deposit only enough material for the desired pattern while subtractive methods deposit a blanket layer of material and remove the majority of it to define the pattern. Two subtractive methods for organic TFTs include photolithography and screen printing. Photolithography is a high-resolution, subtractive method for patterning, and is sometimes used to make complex circuits and displays with organic materials. An additive method sometimes used for fabrication of organic light emitting diodes, metal-organic-metal diodes, and TFTs is inkjet printing. Inkjet printing sometimes maintains registration by digital-image processing and precise spatial control of deposition.
Generally, in a transistor, the source pad and the drain pad are configured in coplanar geometry. That is, the source pad and the drain pad are positioned over the gate electrode and under the semiconductor. Also, the source pad and the drain pad are sometimes configured in a staggered geometry. That is, the source and the drain pad are located over the semiconductor.